Four-membered Carbocyclic Systems

Reisenauer, and H. A. Freitag, Tetrahedron Letters, 1978, 121 Y. Kobayashi, I. Kumadaki, A. Ohsawa, Y. Hanzawa, M. Honda, W. Migashita, and Y. litaka. Tetrahedron Letters, 1977,1795. 

All five oxidation states in the reversible redox system involving the [4]radi-alene (39) and the cyclobutadiene (40) have been observed. As expected.  

Further evidence that butalene (41) is produced from the chloro-Dewarben-zene (42) with base comes from the use of a methyl-labelled analogue. The final distribution of the label reveals that about half of the reaction proceeds through a butalene.  

A comprehensive review of cyclobutadiene-metal complexes has appeared. The first bi(cyclobutadiene)nickel complex of the sandwich type has been reported. r-Bonded intermediates (43) have been isolated at low temperature from 

Martin, M. Hekman, G. Rist, A. Sauter, and D. Bellas, Angew. Chem. Internal. Edn., 1977,16, 406. 

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Four-membered carbocyclic ring systems are commonly formed by cycloaddition of electrophilic alkenes, ketenes and arynes to enamines. Since cycloaddition reactions of enamines are dealt with in Chapter 18 these reactions will only be mentioned briefly here. 

The available C— H coupling data for four-membered carbocyclic ring systems have been summarised by Fleming and Williams. The values of coupling constants can provide a qualitative... 

Hudlicky T, Reed JW (1991) Rearrangements of vinyl cyclopropane and related systems. In Trost BM (ed) Comprehensive organic synthesis, vol 5. Pergamon Press, Oxford, p 899 Hudlicky T, Becker DA, Fan RL, Kozhushkov S (1997) Carbocyclic three-and four-member-ed ring compounds. In de Meijere A (ed) Houben-Weyl methods of organic chemistry, vol El7c. Thieme, Stuttgart, p 2538... 

Four distinct cyclization modes may be possible endo-endo, endo-exo, exo-endo and exo-exo. As before, the first two modes of cyclization produce heterocycles (309, 310) directly (equation 113) while the other two cyclizations give imine-carbocycles (311, 312) (equation 114). Five- or srx-membered cycles may be easily produced directly by this strategy. A wide variety of structurally different hetero- and carbocyclic systems can be obtained. 

The next four procedures describe the regioselective preparation of bicyclic ring systems, specifically, condensed five-membered carbocyclic derivatives. A large... 

A number of metal complexes catalyses specific alkyne polymerizations, giving rise to four-, six- or eight-membered carbocyclic rings. The first work in this area was the nickel-catalysed formation of cyclooctatetraene (40) from acetylene by the group of Reppe ", but since then formation of cyclic systems from acetylenes has been found to be also catalysed by molybdenum, cobalt, iridium and tantalum. ... 

Voliime 6 reviews the literature published during 1976. The format of the earlier volumes is retained, with individual chapters on three-membered rings four-membered rings five- and six-membered rings and related fused systems medium-and large-ring compounds and bridged carbocycles. 

Other Four Heteroatoms 2 2 Five or More Heteroatoms Tricyclic Systems Central Carbocyclic Ring with Fused Five-membered Rings Tricyclic Systems Central Carbocyclic Ring with Fused Five- and Six-membered Rings Tricyclic Systems Central Carbocyclic Ring with Fused Six-membered Rings... 

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